The transcriptional profile of mesenchymal stem cell populations in primary osteoporosis is distinct and shows overexpression of osteogenic inhibitors

A novel miR-466l-3p/FGF23 axis promotes osteogenic differentiation of human bone marrow mesenchymal stem cells

BACKGROUND

MicroRNAs (miRNAs) regulate osteogenic differentiation processes and influence the development of osteoporosis (OP). This study aimed to investigate the potential role of miR-466 l-3p in OP.

METHODS

The expression levels of miR-466 l-3p and fibroblast growth factor 23 (FGF23) were quantified in the trabeculae of the femoral neck of 40 individuals with or without OP using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The impact of miR-466 l-3p or FGF23 expression on cell proliferation and the expression levels of runt-related transcription factor 2 (RUNX2), type I collagen (Col1), osteocalcin (OCN), osterix (OSX) and dentin matrix protein 1 (DMP1) was quantified in human bone marrow mesenchymal stem cells (hBMSCs) overexpressing miR-466 l-3p. Furthermore, alkaline phosphatase (ALP) staining and alizarin red staining were performed to measure ALP activity and the levels of calcium deposition, respectively. In addition, bioinformatics analysis, luciferase reporter assays, and RNA pull-down assays were conducted to explore the molecular mechanisms underlying the effects of miR-466 l-3p and FGF23 in osteogenic differentiation of hBMSCs.

RESULTS

The expression levels of miR-466 l-3p were significantly lower in femoral neck trabeculae of patients with OP than in the control cohort, whereas FGF23 levels exhibited the opposite trend. Furthermore, miR-466 l-3p levels were upregulated and FGF23 levels were downregulated in hBMSCs during osteogenic differentiation. Moreover, the high miR-466 l-3p expression enhanced the mRNA expression of RUNX2, Col1, OCN, OSX and DMP1, as well as cell proliferation, ALP activity, and calcium deposition in hBMSCs. FGF23 was found to be a direct target of miR-466 l-3p. FGF23 overexpression downregulated the expression of osteoblast markers and inhibited the osteogenic differentiation induced by miR-466 l-3p overexpression. qRT-PCR and Western blot assays showed that miR-466 l-3p overexpression decreased the expression levels of mRNAs and proteins associated with the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway, whereas FGF23 upregulation exhibited the opposite trend.

CONCLUSION

In conclusion, these findings suggest that miR-466 l-3p enhances the osteogenic differentiation of hBMSCs by suppressing FGF23 expression, ultimately preventing OP.

Exploring the effects of naringin on oxidative stress-impaired osteogenic differentiation via the Wnt/β-catenin and PI3K/Akt pathways

This study aimed to explore naringin's potential to promote the osteogenic differentiation of MC3T3-E1 under oxidative stress. It delved into Nar's connection with the Wnt/β-catenin and PI3K/Akt signaling pathways. Initially, 2911 OP-related genes were analyzed, revealing close ties with the PI3K/Akt and Wnt pathways alongside oxidative stress. Nar's potential targets-ESR1, HSP90AA1, and ESR2-were identified through various databases and molecular docking studies confirmed Nar's affinity with ESR1 and HSP90AA1. Experiments established optimal concentrations for Nar and H2O2. H2O2 at 0.3 mmol/L damaged MC3T3-E1 cells, alleviated by 0.1 µmol/L Nar. Successful establishment of oxidative stress models was confirmed by DCFH-DA probe and NO detection. Nar exhibited the ability to enhance osteogenic differentiation, counteracting oxidative damage. It notably increased osteoblast-related protein expression in MC3T3-E1 cells under oxidative stress. The study found Nar's positive influence on GSK-3β phosphorylation, β-catenin accumulation, and pathway-related protein expression, all critical in promoting osteogenic differentiation. The research concluded that Nar effectively promotes osteogenic differentiation in MC3T3-E1 cells under oxidative stress. It achieved this by activating the Wnt/β-catenin and PI3K/Akt pathways, facilitating GSK-3β phosphorylation, and enhancing β-catenin accumulation, pivotal in osteogenesis.

Cinobufotalin prevents bone loss induced by ovariectomy in mice through the BMPs/SMAD and Wnt/β-catenin signaling pathways

BACKGROUND

Osteoporosis is a chronic bone disease characterized by bone loss and decreased bone strength. However, current anti-resorptive drugs carry a risk of various complications. The deep learning-based efficacy prediction system (DLEPS) is a forecasting tool that can effectively compete in drug screening and prediction based on gene expression changes. This study aimed to explore the protective effect and potential mechanisms of cinobufotalin (CB), a traditional Chinese medicine (TCM), on bone loss.

METHODS

DLEPS was employed for screening anti-osteoporotic agents according to gene profile changes in primary osteoporosis. Micro-CT, histological and morphological analysis were applied for the bone protective detection of CB, and the osteogenic differentiation/function in human bone marrow mesenchymal stem cells (hBMMSCs) were also investigated. The underlying mechanism was verified using qRT-PCR, Western blot (WB), immunofluorescence (IF), etc. RESULTS: A safe concentration (0.25 mg/kg in vivo, 0.05 μM in vitro) of CB could effectively preserve bone mass in estrogen deficiency-induced bone loss and promote osteogenic differentiation/function of hBMMSCs. Both BMPs/SMAD and Wnt/β-catenin signaling pathways participated in CB-induced osteogenic differentiation, further regulating the expression of osteogenesis-associated factors, and ultimately promoting osteogenesis.

CONCLUSION

Our study demonstrated that CB could significantly reverse estrogen deficiency-induced bone loss, further promoting osteogenic differentiation/function of hBMMSCs, with BMPs/SMAD and Wnt/β-catenin signaling pathways involved.

RNA sequencing-based approaches to identifying disulfidptosis-related diagnostic clusters and immune landscapes in osteoporosis

Disulfidptosis, a newly recognized cell death triggered by disulfide stress, has garnered attention for its potential role in osteoporosis (OP) pathogenesis. Although sulfide-related proteins are reported to regulate the balance of bone metabolism in OP, the precise involvement of disulfidptosis regulators remains elusive. Herein, leveraging the GSE56815 dataset, we conducted an analysis to delineate disulfidptosis-associated diagnostic clusters and immune landscapes in OP. Subsequently, vertebral bone tissues obtained from OP patients and controls were subjected to RNA sequencing (RNA-seq) for the validation of key disulfidptosis gene expression. Our analysis unveiled seven significant disulfidptosis regulators, including FLNA, ACTB, PRDX1, SLC7A11, NUBPL, OXSM, and RAC1, distinguishing OP samples from controls. Furthermore, employing a random forest model, we identified four diagnostic disulfidptosis regulators including FLNA, SLC7A11, NUBPL, and RAC1 potentially predictive of OP risk. A nomogram model integrating these four regulators was constructed and validated using the GSE35956 dataset, demonstrating promising utility in clinical decision-making, as affirmed by decision curve analysis. Subsequent consensus clustering analysis stratified OP samples into two different disulfidptosis subgroups (clusters A and B) using significant disulfidptosis regulators, with cluster B exhibiting higher disulfidptosis scores and implicating monocyte immunity, closely linked to osteoclastogenesis. Notably, RNA-seq analysis corroborated the expression patterns of two disulfidptosis modulators, PRDX1 and OXSM, consistent with bioinformatics predictions. Collectively, our study sheds light on disulfidptosis patterns, offering potential markers and immunotherapeutic avenues for future OP management.

Identification of PKM2 as a pyroptosis-related key gene aggravates senile osteoporosis via the NLRP3/Caspase-1/GSDMD signaling pathway

BACKGROUNDS

Senile osteoporosis-alternatively labeled as skeletal aging-encompasses age-induced bone deterioration and loss of bone microarchitecture. Recent studies have indicated a potential association between senile osteoporosis and chronic systemic inflammation, and pyroptosis in bone marrow-derived mesenchymal stem cells is speculated to contribute to bone loss and osteoporosis. Therefore, targeting pyroptosis in stem cells may be a potential therapeutic strategy for treating osteoporosis.

METHODS

Initially, we conducted bioinformatics analysis to screen the GEO databases to identify the key gene associated with pyroptosis in senile osteoporosis. Next, we analyzed the relationship between altered proteins and clinical data. In vitro experiments were then performed to explore whether the downregulation of PKM2 expression could inhibit pyroptosis. Additionally, an aging-related mouse model of osteoporosis was established to validate the efficacy of a PKM2 inhibitor in alleviating osteoporosis progression.

RESULTS

We identified PKM2 as a key gene implicated in pyroptosis in senile osteoporosis patients through bioinformatics analysis. Further analyses of bone marrow and stem cells demonstrated significant PKM2 overexpression in senile osteoporosis patients. Silencing PKM2 expression inhibited pyroptosis in senile stem cells, of which the osteogenesis potential and angiogenic function were also primarily promoted. Moreover, the results in vivo demonstrated that administering PKM2 inhibitors suppressed pyroptosis in senile osteoporosis mice and mitigated senile osteoporosis progression.

CONCLUSION

Our study uncovered PKM2, a key pyroptosis marker of bone marrow mesenchymal stem cells in senile osteoporosis. Shikonin, a PKM2 inhibitor, was then identified as a potential drug candidate for the treatment of osteoporosis.

IFT20 and WWTR1 govern bone homeostasis via synchronously regulating the expression and stability of TβRII in osteoblast lineage cells

Balance of bone and marrow fat formation is critical for bone homeostasis. The imbalance of bone homeostasis will cause various bone diseases, such as osteoporosis. However, the precise mechanisms governing osteoporotic bone loss and marrow adipose tissue (MAT) accumulation remain poorly understood. By analysis of publicly available databases from bone samples of osteoporosis patients, we found that the expression of intraflagellar transport 20 (IFT20) and WW domain containing transcription regulator 1 (WWTR1) were significantly downregulated in osteoblast lineage cells. Additionally, we found that double deletions of IFT20 and WWTR1 in osteoblasts resulted in a significant accumulation of MAT and bone loss. Moreover, IFT20 and WWTR1 deficiency in osteoblasts exacerbated bone-fat imbalance in ovariectomy (OVX)- and high-fat-diet (HFD)-induced osteoporosis mouse models. Mechanistically, we found that deletions of IFT20 and WWTR1 in osteoblasts synergistically inhibited osteogenesis and promoted adipogenesis and osteoclastogenesis. We also found that IFT20 interacted with TGF-β receptor type II (TβRII) to enhance TβRII stability by blocking c-Cbl-mediated ubiquitination and degradation of TβRII. WWTR1 transcriptionally upregulated TβRII expression by directly binding its promoter. These findings indicate that targeting IFT20/WWTR1 may be a potential therapeutic strategy for the treatment of osteoporosis.

Mesenchymal stem cell-based therapy for osteoporotic bones: Effects of the interaction between cells from healthy and osteoporotic rats on osteoblast differentiation and bone repair

AIMS

Cell therapy utilizing mesenchymal stem cells (MSCs) from healthy donors (HE-MSCs) is a promising strategy for treating osteoporotic bone defects. This study investigated the effects of interaction between HE-MSCs and MSCs from osteoporotic donors (ORX-MSCs) on osteoblast differentiation of MSCs and of HE-MSCs on bone formation in calvarial defects of osteoporotic rats.

MATERIALS AND METHODS

Osteoporosis was induced by orchiectomy (ORX) and its effects on the bone were evaluated by femur microtomography (μCT) and osteoblast differentiation of bone marrow MSCs. HE- and ORX-MSCs were cocultured, and osteoblast differentiation was evaluated using genotypic and phenotypic parameters. HE-MSCs were injected into the calvarial defects of osteoporotic rats, and bone formation was evaluated by μCT, histology, and gene expression of osteoblast markers.

KEY FINDINGS

ORX-induced osteoporosis was revealed by reduced bone morphometric parameters and osteoblast differentiation in ORX-MSCs. HE-MSCs partially recovered the osteogenic potential of ORX-MSCs, whereas HE-MSCs were mildly affected by ORX-MSCs. Additionally, the bone morphogenetic protein and wingless-related integration site signaling pathway components were similarly modulated in cocultures involving ORX-MSCs. HE-MSCs induced meaningful bone formation, highlighting the effectiveness of cell therapy even in osteoporotic bones.

SIGNIFICANCE

These results provide new perspectives on the development of cell-based therapies to regenerate bone defects in patients with disorders that affect bone tissue.

Nanoplastic impact on bone microenvironment: A snapshot from murine bone cells

Our world is made of plastic. Plastic waste deeply affects our health entering the food chain. The degradation and/or fragmentation of plastics due to weathering processes result in the generation of nanoplastics (NPs). Only a few studies tested NPs effects on human health. NPs toxic actions are, in part, mediated by oxidative stress (OS) that, among its effects, affects bone remodeling. This study aimed to assess if NPs influence skeleton remodeling through OS. Murine bone cell cultures (MC3T3-E1 preosteoblasts, MLOY-4 osteocyte-like cells, and RAW264.7 pre-osteoclasts) were used to test the NPs detrimental effects on bone cells. NPs affect cell viability and induce ROS production and apoptosis (by caspase 3/7 activation) in pre-osteoblasts, osteocytes, and pre-osteoclasts. NPs impair the migration capability of pre-osteoblasts and potentiate the osteoclastogenesis of preosteoclasts. NPs affected the expression of genes related to inflammatory and osteoblastogenic pathways in pre-osteoblasts and osteocytes, related to the osteoclastogenic commitment of pre-osteoclasts. A better understanding of the impact of NPs on bone cell activities resulting in vivo in impaired bone turnover could give more information on the possible toxicity consequence of NPs on bone mass and the subsequent public health problems, such as bone disease.

Identification and validation of iron metabolism genes in osteoporosis

BACKGROUND

Osteoporosis is the most common metabolic bone disease in humans. Exploring the expression difference of iron metabolism-related genes in osteoporosis can provide a new target for diagnosis and treatment.

METHODS

First, we used online databases to identify differentially expressed genes (DEGs) related to iron metabolism in patients with osteoporosis. The differential genes were comprehensively analyzed by bioinformatics method (GO, KEGG, GSEA, immune infiltration analysis, PPI). The expression levels of hub genes and important signaling pathways were verified by qRT-PCR and Western blotting.

RESULTS

A total of 23 iron metabolism-related genes with significant differences were identified, which were enriched in "regulation of protein dephosphorylation" and "negative regulation of protein dephosphorylation". The GSEA results, heme metabolism and Myc targets v1 were among the top two pathways, both upregulated. The immune infiltration analysis revealed that the expressions of genes such as ABCA5, D2HGDH, GNAI2, and CTSW were correlated with the infiltration degree of significantly different cells. The PPI network contained 12 differentially expressed iron metabolism-related genes. Additionally, YWHAE, TGFB1, PPP1R15A, TOP2A, and CALR were mined as hub genes using the Cytoscape software. qRT PCR showed that the expression of TGF-β1, YWHAE, TOP2A and CALR increased. We also verified the expression of related proteins and genes in the oxidative stress signaling pathway by qRT PCR and Western blotting. The results showed that Mob1, YAP and TAZ molecules were highly expressed at the gene and protein levels.

CONCLUSIONS

These differentially expressed iron metabolism-related genes could provide new potential targets for the diagnosis and treatment of osteoporosis.

Systems genetics and bioinformatics analyses using ESR1-correlated genes identify potential candidates underlying female bone development

Estrogen receptor α (ESR1) is involved in E2 signaling and plays a major role in postmenopausal bone loss. However, the molecular network underlying ESR1 has not been explored. We used systems genetics and bioinformatics to identify important genes associated with Esr1 in postmenopausal bone loss. We identified ~2300 Esr1-coexpressed genes in female BXD bone femur, functional analysis of which revealed 'osteoblast signaling' as the most enriched pathway. PPI network led to the identification of 25 'female bone candidates'. The gene-regulatory analysis revealed RUNX2 as a key TF. ANKRD1 and RUNX2 were significantly different between osteoporosis patients and healthy controls. Sp7, Col1a1 and Pth1r correlated with multiple femur bone phenotypes in BXD mice. miR-3121-3p targeted Csf1, Ankrd1, Sp7 and Runx2. β-estradiol treatment markedly increased the expression of these candidates in mouse osteoblast. Our study revealed that Esr1-correlated genes Ankrd1, Runx2, Csf1 and Sp7 may play important roles in female bone development.

The age-related characteristics in bone microarchitecture, osteoclast distribution pattern, functional and transcriptomic alterations of BMSCs in mice

Deteriorated age-related bone loss is the hallmarks of skeletal aging. However, how the aging of bone marrow mesenchymal stem cells (BMSCs) and osteoclasts are linked to the bone microstructure degeneration is not yet very clear. In this study, the characteristics of age-related bone loss, distribution patterns of osteoclasts, functional and transcriptomic alterations of BMSCs, hub genes responsible for BMSCs senescence, were analyzed. Our study revealed an age-related declined trends in trabecular and cortical bones of femur, tibia and lumbar vertebra in mice, which was accompanied by a shift from the trabecular to cortical bones in osteoclasts. Additionally, middle-aged or aged mice exhibited remarkably reduced dynamic bone formation capacities, along with reversed osteogenic-adipogenic differentiation potentials in BMSCs. Finally, transcriptomic analysis indicated that aging-related signaling pathways were significantly activated in BMSCs from aged mice (e.g., cellular senescence, p53 signaling pathway, etc.). Also, weighted correlation network analysis (WGCNA) and venn diagram analysis based on our RNA-Seq data and GSE35956 dataset revealed the critical role of PTPN1 in BMSCs senescence. Targeted inhibition of PTP1B with AAV-Ptpn1-RNAi dramatically postponed age-related bone loss in middle-aged mice. Collectively, our study has uncovered the age-dependent cellular characteristics in BMSCs and osteoclasts underlying progressive bone loss with advancing age.

BushenHuoxue formula promotes osteogenic differentiation via affecting Hedgehog signaling pathway in bone marrow stem cells to improve osteoporosis symptoms

BACKGROUND

The BushenHuoxue formula (BSHX) has been previously demonstrated to ameliorate osteoporosis, but the mechanisms underlying this phenomenon are currently unclear. The present study aims at investigating the mechanisms that BSHX induces osteogenesis.

METHODS

We established an osteoporosis model in rats by bilateral ovariectomy and then treated the rats with an osteogenic inducer (dexamethasone, β-sodium glycerophosphate and Vitamin C) and BSHX. After that, bone marrow density and histopathological bone examination were evaluated by using HE staining and immunohistochemistry, respectively. We also assessed the differentiation of bone marrow mesenchymal stem cells (BMSCs) into osteoblasts by using immunofluorescence staining. ALP, BMP, and COL1A1 levels were determined by ELISA. We identified genes involved in pathogenesis of osteoporosis through Gene Expression Omnibus (GEO) database and subsequently selected Hedgehog signaling-related genes Shh, Ihh, Gli2, and Runx2 for assessment via qRT-PCR and ELISA, Western blotting. Network pharmacology analysis was performed to identify bioactive metabolites of BSHX.

RESULTS

BSHX treatment in osteoporosis model rats promoted tightening of the morphological structure of the trabecular bone and increased the bone mineral density (BMD). BSHX also increased levels of osteoblast makers ALP, BMP, and COL1A1. Additionally, bioinformatics analysis of the GEO dataset showed that Hedgehog signaling pathway was involved in pathogenesis of osteoporosis, especially related genes Shh, Ihh, Gli2, and Runx2. Remarkably, BHSX upregulated these genes indispensably involved in the osteogenesis-related Hedgehog signaling pathway in both bone tissue and BMSCs. Importantly, we identified that quercetin was the active compounds that involved in the mechanism of BSHX-improved OP via affecting Hedgehog-related genes.

CONCLUSION

Our results indicate that BSHX promotes osteogenesis by improving BMSC differentiation into osteoblasts via increased expression of Hedgehog signaling-related genes Shh, Ihh, Gli2, and Runx2, and quercetin was the bioactive compound of BSHX.

Ataluren prevented bone loss induced by ovariectomy and aging in mice through the BMP-SMAD signaling pathway

Both estrogen deficiency and aging may lead to osteoporosis. Developing novel drugs for treating osteoporosis is a popular research direction. We screened several potential therapeutic agents through a new deep learning-based efficacy prediction system (DLEPS) using transcriptional profiles for osteoporosis. DLEPS screening led to a potential novel drug examinee, ataluren, for treating osteoporosis. Ataluren significantly reversed bone loss in ovariectomized mice. Next, ataluren significantly increased human bone marrow-derived mesenchymal stem cell (hBMMSC) osteogenic differentiation without cytotoxicity, indicated by the high expression index of osteogenic differentiation genes (OCN , BGLAP, ALP, COL1A, BMP2, RUNX2). Mechanistically, ataluren exerted its function through the BMP-SMAD pathway. Furthermore, it activated SMAD phosphorylation but osteogenic differentiation was attenuated by BMP2-SMAD inhibitors or small interfering RNA of BMP2. Finally, ataluren significantly reversed bone loss in aged mice. In summary, our findings suggest that the DLEPS-screened ataluren may be a therapeutic agent against osteoporosis by aiding hBMMSC osteogenic differentiation.

Regulation and Function of FOXC1 in Osteoblasts

Estrogens, which bind to estrogen receptor alpha (ERα), are important for proper bone mineral density. When women go through menopause, estrogen levels decrease, and there is a decrease in bone quality, along with an increased risk for fractures. We previously identified an enhancer near FOXC1 as the most significantly enriched binding site for estrogen receptor alpha (ERα) in osteoblasts. FOXC1 is a transcription factor belonging to a large group of proteins known as forkhead box genes and is an important regulator of bone formation. Here, we demonstrate that 17β-estradiol (E2) increases the mRNA and protein levels of FOXC1 in primary mouse and human osteoblasts. GATA4 is a pioneer factor for ERα and it is also recruited to enhancers near Foxc1. Knockdown of Gata4 in mouse osteoblasts in vitro decreases Foxc1 expression as does knockout of Gata4 in vivo. Functionally, GATA4 and FOXC1 interact and regulate osteoblast proteins such as RUNX2, as demonstrated by ChIP-reChIP and luciferase assays. The most enriched motif in GATA4 binding sites from ChIP-seq is for FOXC1, supporting the notion that GATA4 and FOXC1 cooperate in regulating osteoblast differentiation. Together, these data demonstrate the interactions of the transcription factors ERα, GATA4, and FOXC1 to regulate each other's expression and other osteoblast differentiation genes.

Identifying Crucial Biomarkers in Osteoporosis and Ulcerative Colitis Through Bioinformatics Analysis of Co-expressed Genes

Osteoporosis (OP) and ulcerative colitis (UC), prevalent immune diseases, exert a substantial socioeconomic impact globally. This study identifies biomarkers for these diseases, paving the way for in-depth research. Initially, the Gene Expression Omnibus (GEO) database was employed to analyze datasets GSE35958 and GSE87466. This analysis aimed to pinpoint co-expression differential genes (DEGs) between OP and UC. Subsequently, the Metascape database facilitated the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of these DEGs' co-expression. For network construction and visualization, the STRING11.5 database along with Cytoscape 3.7.2 (Cytoscape Team, USA) were utilized to create a protein-protein interaction (PPI) network. Moreover, Cytoscape's cytoHubba plugin was instrumental in identifying the central genes, known as hub genes. In the datasets GSE35958 and GSE87466, 156 co-expressed DEGs were discovered. The PPI network, constructed using STRING11.5 and Cytoscape 3.7.2, comprises 96 nodes and 222 connections. Notably, seven hub genes were identified, namely COL6A1, COL6A2, BGN, NID1, PLAU, TGFB1, and PLAUR. These DEGs were predominantly enriched in pathways such as extracellular matrix organization and collagen-containing extracellular matrix, as per GO analysis. For diagnostic model construction and hub gene validation, datasets GSE56815 and GSE107499 from the GEO database were employed. The top five hub genes were validated. In conclusion, the hub genes identified in this study played a significant role in the early diagnosis, prevention, and treatment of OP and UC. Furthermore, they provide fresh insights into the underlying mechanisms of these diseases' development and progression.

Releasing YAP dysfunction-caused replicative toxicity rejuvenates mesenchymal stem cells

Hippo-independent YAP dysfunction has been demonstrated to cause chronological aging of stromal cells by impairing the integrity of nuclear envelope (NE). In parallel with this report, we uncover that YAP activity also controls another type of cellular senescence, the replicative senescence in in vitro expansion of mesenchymal stromal cells (MSCs), but this event is Hippo phosphorylation-dependent, and there exist another NE integrity-independent downstream mechanisms of YAP. Specifically, Hippo phosphorylation causes reduced nuclear/active YAP and then decreases the level of YAP protein in the proceeding of replicative senescence. YAP/TEAD governs RRM2 expression to release replicative toxicity (RT) via licensing G1/S transition. Besides, YAP controls the core transcriptomics of RT to delay the onset of genome instability and enhances DNA damage response/repair. Hippo-off mutations of YAP (YAPS127A/S381A ) satisfactorily release RT via maintaining cell cycle and reducing genome instability, finally rejuvenating MSCs and restoring their regenerative capabilities without risks of tumorigenesis.

Immune-related gene IL17RA as a diagnostic marker in osteoporosis

Objectives: Bone immune disorders are major contributors to osteoporosis development. This study aims to identify potential diagnostic markers and molecular targets for osteoporosis treatment from an immunological perspective. Method: We downloaded dataset GSE56116 from the Gene Expression Omnibus database, and identified differentially expressed genes (DEGs) between normal and osteoporosis groups. Subsequently, differentially expressed immune-related genes (DEIRGs) were identified, and a functional enrichment analysis was performed. A protein-protein interaction network was also constructed based on data from STRING database to identify hub genes. Following external validation using an additional dataset (GSE35959), effective biomarkers were confirmed using RT-qPCR and immunohistochemical (IHC) staining. ROC curves were constructed to validate the diagnostic values of the identified biomarkers. Finally, a ceRNA and a transcription factor network was constructed, and a Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis was performed to explore the biological functions of these diagnostic markers. Results: In total, 307 and 31 DEGs and DEIRGs were identified, respectively. The enrichment analysis revealed that the DEIRGs are mainly associated with Gene Ontology terms of positive regulation of MAPK cascade, granulocyte chemotaxis, and cytokine receptor. protein-protein interaction network analysis revealed 10 hub genes: FGF8, KL, CCL3, FGF4, IL9, FGF9, BMP7, IL17RA, IL12RB2, CD40LG. The expression level of IL17RA was also found to be significantly high. RT-qPCR and immunohistochemical results showed that the expression of IL17RA was significantly higher in osteoporosis patients compared to the normal group, as evidenced by the area under the curve Area Under Curve of 0.802. Then, we constructed NEAT1-hsa-miR-128-3p-IL17RA, and SNHG1-hsa-miR-128-3p-IL17RA ceRNA networks in addition to ERF-IL17RA, IRF8-IL17RA, POLR2A-IL17RA and ERG-IL17RA transcriptional networks. Finally, functional enrichment analysis revealed that IL17RA was involved in the development and progression of osteoporosis by regulating local immune and inflammatory processes in bone tissue. Conclusion: This study identifies the immune-related gene IL17RA as a diagnostic marker of osteoporosis from an immunological perspective, and provides insight into its biological function.

Integration of Transcriptome and MicroRNA Profile Analysis of iMSCs Defines Their Rejuvenated State and Conveys Them into a Novel Resource for Cell Therapy in Osteoarthritis

Although MSCs grant pronounced potential for cell therapies, several factors, such as their heterogeneity restrict their use. To overcome these limitations, iMSCs (MSCs derived from induced pluripotent stem cells (iPSCs) have attracted attention. Here, we analyzed the transcriptome of MSCs, iPSCs and iMSCs derived from healthy individuals and osteoarthritis (OA) patients and explored miRNA-mRNA interactions during these transitions. We performed RNA-seq and gene expression comparisons and Protein-Protein-Interaction analysis followed by GO enrichment and KEGG pathway analyses. MicroRNAs' (miRNA) expression profile using miRarrays and differentially expressed miRNA's impact on regulating iMSCs gene expression was also explored. Our analyses revealed that iMSCs derivation from iPSCs favors the expression of genes conferring high proliferation, differentiation, and migration properties, all of which contribute to a rejuvenated state of iMSCs compared to primary MSCs. Additionally, our exploration of the involvement of miRNAs in this rejuvenated iMSCs transcriptome concluded in twenty-six miRNAs that, as our analysis showed, are implicated in pluripotency. Notably, the identified here interactions between hsa-let7b/i, hsa-miR-221/222-3p, hsa-miR-302c, hsa-miR-181a, hsa-miR-331 with target genes HMGA2, IGF2BP3, STARD4, and APOL6 could prove to be the necessary tools that will convey iMSCs into the ideal mean for cell therapy in osteoarthritis.

CUL4B orchestrates mesenchymal stem cell commitment by epigenetically repressing KLF4 and C/EBPδ

Dysregulated lineage commitment of mesenchymal stem cells (MSCs) contributes to impaired bone formation and an imbalance between adipogenesis and osteogenesis during skeletal aging and osteoporosis. The intrinsic cellular mechanism that regulates MSC commitment remains unclear. Here, we identified Cullin 4B (CUL4B) as a critical regulator of MSC commitment. CUL4B is expressed in bone marrow MSCs (BMSCs) and downregulated with aging in mice and humans. Conditional knockout of Cul4b in MSCs resulted in impaired postnatal skeletal development with low bone mass and reduced bone formation. Moreover, depletion of CUL4B in MSCs aggravated bone loss and marrow adipose accumulation during natural aging or after ovariectomy. In addition, CUL4B deficiency in MSCs reduced bone strength. Mechanistically, CUL4B promoted osteogenesis and inhibited adipogenesis of MSCs by repressing KLF4 and C/EBPδ expression, respectively. The CUL4B complex directly bound to Klf4 and Cebpd and epigenetically repressed their transcription. Collectively, this study reveals CUL4B-mediated epigenetic regulation of the osteogenic or adipogenic commitment of MSCs, which has therapeutic implications in osteoporosis.

USP53 Regulates Bone Homeostasis by Controlling Rankl Expression in Osteoblasts and Bone Marrow Adipocytes

In the skeleton, osteoblasts and osteoclasts synchronize their activities to maintain bone homeostasis and integrity. Investigating the molecular mechanisms governing bone remodeling is critical and helps understand the underlying biology of bone disorders. Initially, we have identified the ubiquitin-specific peptidase gene (Usp53) as a target of the parathyroid hormone in osteoblasts and a regulator of mesenchymal stem cell differentiation. Mutations in USP53 have been linked to a constellation of developmental pathologies. However, the role of Usp53 in bone has never been visited. Here we show that Usp53 null mice have a low bone mass phenotype in vivo. Usp53 null mice exhibit a pronounced decrease in trabecular bone indices including trabecular bone volume (36%) and trabecular number (26%) along with an increase in trabecular separation (13%). Cortical bone parameters are also impacted, showing a reduction in cortical bone volume (12%) and cortical bone thickness (15%). As a result, the strength and mechanical bone properties of Usp53 null mice have been compromised. At the cellular level, the ablation of Usp53 perturbs bone remodeling, augments osteoblast-dependent osteoclastogenesis, and increases osteoclast numbers. Bone marrow adipose tissue volume increased significantly with age in Usp53-deficient mice. Usp53 null mice displayed increased serum receptor activator of NF-κB ligand (RANKL) levels, and Usp53-deficient osteoblasts and bone marrow adipocytes have increased expression of Rankl. Mechanistically, USP53 regulates Rankl expression by enhancing the interaction between VDR and SMAD3. This is the first report describing the function of Usp53 during skeletal development. Our results put Usp53 in display as a novel regulator of osteoblast-osteoclast coupling and open the door for investigating the involvement of USP53 in pathologies. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Causal effect of polyunsaturated fatty acids on bone mineral density and fracture

Background

Polyunsaturated fatty acids (PUFAs) are closely related to osteoporosis. To test their causal relationship, we conducted a Mendelian randomization (MR) analysis.

Methods

We analyzed the causal relationship between four PUFAs measures, n-3 PUFAs (n-3), n-6 PUFAs (n-6), the ratio of n-3 PUFAs to total fatty acids (n-3 pct), and the ratio of n-6 PUFAs to n-3 PUFAs (n-6 to n-3), and five measures of osteoporosis, including estimated bone mineral density (eBMD), forearm (FA) BMD, femoral neck (FN) BMD, lumbar spine (LS) BMD, and fracture, using two-sample MR analysis. In order to verify the direct effect between PUFAs and BMD, we chose interleukin-6 (IL-6), tumor necrosis factor-β (TNF-β), and bone morphogenetic proteins 7 (BMP-7), three markers or cytokines strongly related to BMD, as possible confounding factors, and analyzed the possible causal relationships between them and PUFAs or BMD by MR. Inverse variance weighting (IVW), MR-Egger, weighted and weighted median were conducted. MR Pleiotropy RESidual Sum and Outlier (MR-PRESSO) and MR-Egger regression methods were used to evaluate the potential pleiotropy of instrumental variables (IVs) and outliers were identified by MR-PRESSO. Cochran's Q statistic was used to detect the heterogeneity among IVs. Leave-one-out sensitivity analysis was used to find SNPs that have a significant impact on the results. All results were corrected by the Bonferroni correction.

Results

The IVW results showed that n-3 PUFAs (OR = 1.030, 95% CI: 1.013, 1.047, P = 0.001) and n-6 PUFAs (OR = 1.053, 95% CI: 1.034, 1.072, P < 0.001) were positively correlated with eBMD, while n-6 to n-3 (OR = 0.947, 95% CI: 0.924, 0.970, P < 0.001) were negatively correlated with eBMD. These casual relationships still existed after Bonferroni correction. There were positive effects of n-3 PUFAs on FA BMD (OR = 1.090, 95% CI: 1.011, 1.176, P = 0.025) and LS BMD (OR = 1.056, 95% CI: 1.011, 1.104, P = 0.014), n-3 pct on eBMD (OR = 1.028, 95% CI: 1.002, 1.055, P = 0.035) and FA BMD (OR = 1.090, 95% CI: 1.011, 1.174, P = 0.025), n-6 to n-3 on LS BMD (OR = 1.071, 95% CI: 1.021, 1.124, P = 0.005); negative effects of n-3 pct on fracture (OR = 0.953, 95% CI: 0.918, 0.988, P = 0.009) and n-6 to n-3 on FA BMD (OR = 0.910, 95% CI: 0.837, 0.988, P = 0.025). However, these causal effects all disappeared after Bonferroni correction (all P > 0.0025). None of IL-6, TNF-β, and BMP-7 had a causal effect on PUFA and BMD simultaneously (all P > 0.05).

Conclusion

Evidence from this MR study supports the genetically predicted causal effects of n-3, n-6, n-3 pct, and n-6 to n-3 on eBMD. In addition, n-3 not only associate with FA BMD and LS BMD through its own level and n-6 to n-3, but also link to fracture through n-3 pct.

Unveiling the transcriptomic landscape and the potential antagonist feedback mechanisms of TGF-β superfamily signaling module in bone and osteoporosis

BACKGROUND

TGF-β superfamily signaling is indispensable for bone homeostasis. However, the global expression profiles of all the genes that make up this signaling module in bone and bone-related diseases have not yet been well characterized.

METHODS

Transcriptomic datasets from human bone marrows, bone marrow-derived mesenchymal stem cells (MSCs) and MSCs of primary osteoporotic patients were used for expression profile analyses. Protein treatments, gene quantification, reporter assay and signaling dissection in MSC lines were used to clarify the interactive regulations and feedback mechanisms between TGF-β superfamily ligands and antagonists. Ingenuity Pathway Analysis was used for network construction.

RESULTS

We identified TGFB1 in the ligand group that carries out SMAD2/3 signaling and BMP8A, BMP8B and BMP2 in the ligand group that conducts SMAD1/5/8 signaling have relatively high expression levels in normal bone marrows and MSCs. Among 16 antagonist genes, the dominantly expressed TGF-β superfamily ligands induced only NOG, GREM1 and GREM2 via different SMAD pathways in MSCs. These induced antagonist proteins further showed distinct antagonisms to the treated ligands and thus would make up complicated negative feedback networks in bone. We further identified TGF-β superfamily signaling is enriched in MSCs of primary osteoporosis. Enhanced expression of the genes mediating TGF-β-mediated SMAD3 signaling and the genes encoding TGF-β superfamily antagonists served as significant features to osteoporosis.

CONCLUSION

Our data for the first time unveiled the transcription landscape of all the genes that make up TGF-β superfamily signaling module in bone. The feedback mechanisms and regulatory network prediction of antagonists provided novel hints to treat osteoporosis. Video Abstract.

Telomere Length and Risk of Incident Fracture and Arthroplasty: Findings From UK Biobank

We investigated independent associations between telomere length and risk of fracture and arthroplasty in UK Biobank participants. Leukocyte telomere length (LTL) was measured in baseline samples using a validated polymerase chain reaction (PCR) method. We used, in men and women separately, Cox proportional hazards models to calculate the hazard ratio (HR) for incident fracture (any, osteoporotic) or arthroplasty (hip or knee) over 1,186,410 person-years of follow-up. Covariates included age, white cell count, ethnicity, smoking, alcohol, physical activity, and menopause (women). In further analyses we adjusted for either estimated bone mineral density (eBMD) from heel quantitative ultrasound, handgrip strength, gait speed, total fat mass (bioimpedance), or blood biomarkers, all measured at baseline (2006-2010). We studied 59,500 women and 51,895 men, mean ± standard deviation (SD) age 56.4 ± 8.0 and 57.0 ± 8.3 years, respectively. During follow-up there were 5619 fractures; 5285 hip and 4261 knee arthroplasties. In confounder-adjusted models, longer LTL was associated with reduced risk of incident knee arthroplasty in both men (HR/SD 0.93; 95% confidence interval [CI], 0.88-0.97) and women (0.92; 95% CI, 0.88-0.96), and hip arthroplasty in men (0.91; 95% CI, 0.87-0.95), but not women (0.98; 95% CI, 0.94-1.01). Longer LTL was weakly associated with reduced risk of any incident fracture in women (HR/SD 0.96; 95% CI, 0.93-1.00) with less evidence in men (0.98; 95% CI, 0.93-1.02). Associations with incident outcomes were not materially altered by adjustment for heel eBMD, grip strength, gait speed, fat mass, or blood biomarker measures. In this, the largest study to date, longer LTL was associated with lower risk of incident knee or hip arthroplasty, but only weakly associated with lower risk of fracture. The relative risks were low at a population level, but our findings suggest that common factors acting on the myeloid and musculoskeletal systems might influence later life musculoskeletal outcomes. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Typing characteristics of metabolism-related genes in osteoporosis

Objective: Osteoporosis is a common musculoskeletal disease. Fractures caused by osteoporosis place a huge burden on global healthcare. At present, the mechanism of metabolic-related etiological heterogeneity of osteoporosis has not been explored, and no research has been conducted to analyze the metabolic-related phenotype of osteoporosis. This study aimed to identify different types of osteoporosis metabolic correlates associated with underlying pathogenesis by machine learning.

Methods: In this study, the gene expression profiles GSE56814 and GSE56815 of osteoporosis patients were downloaded from the GEO database, and unsupervised clustering analysis was used to identify osteoporosis metabolic gene subtypes and machine learning to screen osteoporosis metabolism-related characteristic genes. Meanwhile, multi-omics enrichment was performed using the online Proteomaps tool, and the results were validated using external datasets GSE35959 and GSE7429. Finally, the immune and stromal cell types of the signature genes were inferred by the xCell method.

Results: Based on unsupervised cluster analysis, osteoporosis metabolic genotyping can be divided into three distinct subtypes: lipid and steroid metabolism subtypes, glycolysis-related subtypes, and polysaccharide subtypes. In addition, machine learning SVM identified 10 potentially metabolically related genes, GPR31, GATM, DDB2, ARMCX1, RPS6, BTBD3, ADAMTSL4, COQ6, B3GNT2, and CD9.

Conclusion: Based on the clustering analysis of gene expression in patients with osteoporosis and machine learning, we identified different metabolism-related subtypes and characteristic genes of osteoporosis, which will help to provide new ideas for the metabolism-related pathogenesis of osteoporosis and provide a new direction for follow-up research.

Integrated Analysis of Crucial Genes and miRNAs Associated with Osteoporotic Fracture of Type 2 Diabetes

Purpose. The aim of this study is to explore pathological mechanisms of bone fragility in type 2 diabetes mellitus (T2DM) patients. Methods. Identifying common genes for T2DM and osteoporosis by taking the intersection is shared by the Comparative Toxicogenomics Database (CTD), DISEASES, and GeneCards databases. The differentially expressed genes (DEGs) and the differentially expressed miRNAs (DEMs) were identified by analyzing the Gene Expression Omnibus (GEO) datasets (GSE35958, GSE43950, and GSE70318). FunRich and miRNet were applied to predict potential upstream transcription factors and downstream target genes of candidate DEMs, respectively. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed to explore potential mechanisms using Metascape. Eventually, a miRNA-gene network was constructed by Cytoscape software. Results. 271 common targets and 35 common DEGs between T2DM and osteoporosis were screened out in the above databases, and a total of ten DEMs were obtained in the GSE70318. SP1 was predicted to potentially regulate most of the DEMs. Enrichment analysis showed the PI3K-Akt signaling pathway and AGE-RAGE signaling pathway in diabetic complications may play an important role in diabetic skeletal fragility. Two genes (NAMPT and IGFBP5) were considered as key genes involving in the development of diabetic osteoporosis. Through the construction of the miRNA-gene network, most of the hub genes were found to be potentially modulated by miR-96-5p and miR-7-5p. Conclusion. The study uncovered several important genes, miRNAs, and pathological mechanisms involved in diabetic skeletal fragility, among which the PI3K-Akt signaling pathway and AGE-RAGE signaling pathway in diabetic complications may play important roles.

Immune and stem cell compartments of acetabular and femoral bone marrow in hip osteoarthritis patients

OBJECTIVE

Hip osteoarthritis (OA) affects all components of the osteochondral unit, leading to bone marrow (BM) lesions, and unknown consequences on BM cell functionality. We analyzed the cellular composition in OA-affected acetabula compared to proximal femur shafts obtained of hip OA patients to reveal yet not explored immune and stem cell compartments.

DESIGN

Combining flow cytometry, cellular assays and transcription analyses, we performed extensive ex vivo phenotyping of acetabular BM cells from 18 hip OA patients, comparing them with their counterparts from patient-matched femoral shaft BM samples. Findings were related to differences in skeletal sites and age.

RESULTS

Acetabular BM had a greater frequency of T-lymphocytes, non-hematopoietic cells and colony-forming units fibroblastic potential than femoral BM. The incidence of acetabular CD45⁺CD3⁺ T-lymphocytes increased (95% CI: 0.1770 to 0.0.8416), while clonogenic hematopoietic progenitors declined (95% CI: -0.9023 to -0.2399) with age of patients. On the other side, in femoral BM, we observed higher B-lymphocyte, myeloid and erythroid cell frequencies. Acetabular mesenchymal stromal cells (MSCs) showed a senescent profile associated with the expression of survival and inflammation-related genes. Efficient osteogenic and chondrogenic differentiation was detected in acetabular MSCs, while adipogenesis was more pronounced in their femoral counterparts.

CONCLUSION

Our results suggest that distinctions in BM cellular compartments and MSCs may be due to the influence of the OA-stressed microenvironment, but also acetabular vs femoral shaft-specific peculiarities cannot be excluded. These results bring new knowledge on acetabular BM cell populations and may be addressed as novel pathogenic mechanisms and therapeutic targets in OA.

Identification of osteoporosis based on gene biomarkers using support vector machine

Osteoporosis is a major health concern worldwide. The present study aimed to identify effective biomarkers for osteoporosis detection. In osteoporosis, 559 differentially expressed genes (DEGs) were enriched in PI3K-Akt signaling pathway and Foxo signaling pathway. Weighted gene co-expression network analysis showed that green, pink, and tan modules were clinically significant modules, and that six genes (VEGFA, DDX5, SOD2, HNRNPD, EIF5B, and HSP90B1) were identified as “real” hub genes in the protein–protein interaction network, co-expression network, and 559 DEGs. The sensitivity and specificity of the support vector machine (SVM) for identifying patients with osteoporosis was 100%, with an area under curve of 1 in both training and validation datasets. Our results indicated that the current system using the SVM method could identify patients with osteoporosis.

Fisetin: An Integrated Approach to Identify a Strategy Promoting Osteogenesis

Flavonoids may modulate the bone formation process. Among flavonoids, fisetin is known to counteract tumor growth, osteoarthritis, and rheumatoid arthritis. In addition, fisetin prevents inflammation-induced bone loss. In order to evaluate its favorable use in osteogenesis, we assayed fisetin supplementation in both in vitro and in vivo models and gathered information on nanoparticle-mediated delivery of fisetin in vitro and in a microfluidic system. Real-time RT-PCR, Western blotting, and nanoparticle synthesis were performed to evaluate the effects of fisetin in vitro, in the zebrafish model, and in ex vivo samples. Our results demonstrated that fisetin at 2.5 µM concentration promotes bone formation in vitro and mineralization in the zebrafish model. In addition, we found that fisetin stimulates osteoblast maturation in cell cultures obtained from cleidocranial dysplasia patients. Remarkably, PLGA nanoparticles increased fisetin stability and, consequently, its stimulating effects on RUNX2 and its downstream gene SP7 expression. Therefore, our findings demonstrated the positive effects of fisetin on osteogenesis and suggest that patients affected by skeletal diseases, both of genetic and metabolic origins, may actually benefit from fisetin supplementation.

Osteogenic capacity of mesenchymal stem cells from patients with osteoporotic hip fractures in vivo

PURPOSE

Human mesenchymal stem cells (MSCs) have the ability to differentiate into bone-forming osteoblasts. The aim of this study was to elucidate if MSCs from patients with OP show a senescent phenotype and explore their bone-forming ability in vivo.

MATERIALS AND METHODS

MSCs from patients with OP and controls with osteoarthritis (OA) were implanted into the subcutaneous tissue of immunodeficient mice for histological analysis and expression of human genes by RT-PCR. The expression of senescence-associated phenotype (SASP) genes, as well as p16, p21, and galactosidase, was studied in cultures of MSCs.

RESULTS

In vivo bone formation was evaluated in 103 implants (47 OP, 56 OA). New bone was observed in 45% of the implants with OP cells and 46% of those with OA cells (p = 0.99). The expression of several bone-related genes (collagen, osteocalcin, alkaline phosphatase, sialoprotein) was also similar in both groups. There were no differences between groups in SASP gene expression, p16, and p21 expression, or in senescence-associated galactosidase activity.

CONCLUSION

Senescence markers and the osteogenic capacity in vivo of MSCs from patients with OP are not inferior to that of cells from controls of similar age with OA. This supports the interest of future studies to evaluate the potential use of autologous MSCs from OP patients in bone regeneration procedures.

The m6A demethylase FTO promotes the osteogenesis of mesenchymal stem cells by downregulating PPARG

N⁶-methyladenosine (m⁶A) is the most abundant posttranscriptional methylation modification that occurs in mRNA and modulates the fine-tuning of various biological processes in mammalian development and human diseases. In this study we investigated the role of m⁶A modification in the osteogenesis of mesenchymal stem cells (MSCs), and the possible mechanisms by which m⁶A modification regulated the processes of osteoporosis and bone necrosis. We performed systematic analysis of the differential gene signatures in patients with osteoporosis and bone necrosis and conducted m⁶A-RNA immunoprecipitation (m⁶A-RIP) sequencing to identify the potential regulatory genes involved in osteogenesis. We showed that fat mass and obesity (FTO), a primary m⁶A demethylase, was significantly downregulated in patients with osteoporosis and osteonecrosis. During the differentiation of human MSCs into osteoblasts, FTO was markedly upregulated. Both depletion of FTO and application of the FTO inhibitor FB23 or FB23-2 impaired osteogenic differentiation of human MSCs. Knockout of FTO in mice resulted in decreased bone mineral density and impaired bone formation. PPARG, a biomarker for osteoporosis, was identified as a critical downstream target of FTO. We further revealed that FTO mediated m⁶A demethylation in the 3'UTR of PPARG mRNA, and reduced PPARG mRNA stability in an YTHDF1-dependent manner. Overexpression of PPARG alleviated FTO-mediated osteogenic differentiation of MSCs, whereas knockdown of PPARG promoted FTO-induced expression of the osteoblast biomarkers ALPL and OPN during osteogenic differentiation. Taken together, this study demonstrates the functional significance of the FTO-PPARG axis in promoting the osteogenesis of human MSCs and sheds light on the role of m⁶A modification in mediating osteoporosis and osteonecrosis.

Comparing the efficacy of adipose-derived and bone marrow-derived cells in a rat model of posterolateral lumbar fusion

Although bone marrow-derived mesenchymal stem cells (BMCs) have been widely used in spinal fusion procedures, adipose-derived stem cells (ASCs) offer a number of advantages as an alternative clinical cell source. This study directly compares the efficacy of ASCs and BMCs from the same donor animals to achieve successful fusion when combined with a clinical-grade bone graft substitute in a rat lumbar fusion model. ASCs and BMCs were isolated from the same Lewis donor rats and grown to passage 2 (P2). Single-level bilateral posterolateral intertransverse process lumbar fusion surgery was performed on syngeneic rats divided into three experimental groups: clinical-grade bone graft substitute alone (CBGS); CBGS+ rat ASCs (rASC); and, CBGS+ rat BMCs (rBMC). Eight weeks postoperatively, fusion was evaluated via micro-CT, manual palpation and histology. In vitro analysis of the osteogenic capacity of rBMCs and rASCs was also performed. Results indicated that the average fusion volume in the rASC group was the largest and was significantly larger than the CBGS group. Although the rASC group displayed the highest fusion rates via micro-CT and manual palpation, this difference was not statistically significant. Cell-seeded grafts showed more histological bone formation than cell-free grafts. P2 rASCs and rBMCs displayed similar in vitro osteogenic differentiation capacities. Overall, this study showed that, when combined with a clinical-grade bone graft substitute in a rat model, rASCs cells yielded the largest fusion masses and comparable fusion results to rBMCs. These results add to growing evidence that ASCs provide an attractive alternative to BMCs for spinal fusion procedures.

Identification of Type 2 Diabetes Based on a Ten-Gene Biomarker Prediction Model Constructed Using a Support Vector Machine Algorithm

Background

Type 2 diabetes is a major health concern worldwide. The present study is aimed at discovering effective biomarkers for an efficient diagnosis of type 2 diabetes.

Methods

Differentially expressed genes (DEGs) between type 2 diabetes patients and normal controls were identified by analyses of integrated microarray data obtained from the Gene Expression Omnibus database using the Limma package. Functional analysis of genes was performed using the R software package clusterProfiler. Analyses of protein-protein interaction (PPI) performed using Cytoscape with the CytoHubba plugin were used to determine the most sensitive diagnostic gene biomarkers for type 2 diabetes in our study. The support vector machine (SVM) classification model was used to validate the gene biomarkers used for the diagnosis of type 2 diabetes.

Results

GSE164416 dataset analysis revealed 499 genes that were differentially expressed between type 2 diabetes patients and normal controls, and these DEGs were found to be enriched in the regulation of the immune effector pathway, type 1 diabetes mellitus, and fatty acid degradation. PPI analysis data showed that five MCODE clusters could be considered as clinically significant modules and that 10 genes (IL1B, ITGB2, ITGAX, COL1A1, CSF1, CXCL12, SPP1, FN1, C3, and MMP2) were identified as “real” hub genes in the PPI network using algorithms such as Degree, MNC, and Closeness. The sensitivity and specificity of the SVM model for identifying patients with type 2 diabetes were 100%, with an area under the curve of 1 in the training as well as the validation dataset.

Conclusion

Our results indicate that the SVM-based model developed by us can facilitate accurate diagnosis of type 2 diabetes.

Gene Network Analysis for Osteoporosis, Sarcopenia, Diabetes, and Obesity in Human Mesenchymal Stromal Cells

The systemic gene interactions that occur during osteoporosis and their underlying mechanisms remain to be determined. To this end, mesenchymal stromal cells (MSCs) were analyzed from bone marrow samples collected from healthy individuals (n = 5) and patients with osteoporosis (n = 5). A total of 120 osteoporosis-related genes were identified using RNA-sequencing (RNA-seq) and Ingenuity Pathway Analysis (IPA) software. In order to analyze these genes, we constructed a heatmap of one-way hierarchical clustering and grouped the gene expression patterns of the samples. The MSCs from one control participant showed a similar expression pattern to that observed in the MSCs of three patients with osteoporosis, suggesting that the differentiating genes might be important genetic determinants of osteoporosis. Then, we selected the top 38 genes based on fold change and expression, excluding osteoporosis-related genes from the control participant. We identified a network among the top 38 genes related to osteoblast and osteoclast differentiation, bone remodeling, osteoporosis, and sarcopenia using the Molecule Activity Predictor program. Among them, 25 genes were essential systemic genes involved in osteoporosis. Furthermore, we identified 24 genes also associated with diabetes and obesity, among which 10 genes were involved in a network related to bone and energy metabolism. The study findings may have implications for the treatment and prevention of osteoporosis.

Transcriptomic Response to Acidosis Reveals Its Contribution to Bone Metastasis in Breast Cancer Cells

Bone is the most common site of metastasis in breast cancer. Metastasis is promoted by acidosis, which is associated with osteoporosis. To investigate how acidosis could promote bone metastasis, we compared differentially expressed genes (DEGs) in MDA-MB-231 cancer cells in acidosis, bone metastasis, and bone metastatic tumors. The DEGs were identified using Biojupies and GEO2R. The expression profiles were assessed with Morpheus. The overlapping DEGs between acidosis and bone metastasis were compared to the bulk of the DEGs in terms of the most important genes and enriched terms using CytoHubba and STRING. The expression of the genes in this overlap filtered by secreted proteins was assessed in the osteoporosis secretome. The analysis revealed that acidosis-associated transcriptomic changes were more similar to bone metastasis than bone metastatic tumors. Extracellular matrix (ECM) organization would be the main biological process shared between acidosis and bone metastasis. The secretome genes upregulated in acidosis, bone metastasis, and osteoporosis-associated mesenchymal stem cells are enriched for ECM organization and angiogenesis. Therefore, acidosis may be more important in the metastatic niche than in the primary tumor. Acidosis may contribute to bone metastasis by promoting ECM organization. Untreated osteoporosis could favor bone metastasis through the increased secretion of ECM organization proteins.

Epigenetic aging of the demographically non-aging naked mole-rat

The naked mole-rat (NMR) is an exceptionally long-lived rodent that shows no increase of mortality with age, defining it as a demographically non-aging mammal. Here, we perform bisulfite sequencing of the blood of > 100 NMRs, assessing > 3 million common CpG sites. Unsupervised clustering based on sites whose methylation correlates with age reveals an age-related methylome remodeling, and we also observe a methylome information loss, suggesting that NMRs age. We develop an epigenetic aging clock that accurately predicts the NMR age. We show that these animals age much slower than mice and much faster than humans, consistent with their known maximum lifespans. Interestingly, patterns of age-related changes of clock sites in Tert and Prpf19 differ between NMRs and mice, but there are also sites conserved between the two species. Together, the data indicate that NMRs, like other mammals, epigenetically age even in the absence of demographic aging of this species.

The exceptionally long-lived naked mole-rat is characterized by the lack of increased mortality with aging. Here the authors perform epigenetic studies to show that naked mole-rats epigenetically age despite their non-increasing mortality rate.

Alkbh1-mediated DNA N6-methyladenine modification regulates bone marrow mesenchymal stem cell fate during skeletal aging

Objectives

DNA N6‐methyladenine (N6‐mA) demethylase Alkbh1 participates in regulating osteogenic differentiation of mesenchymal stem cell (MSCs) and vascular calcification. However, the role of Alkbh1 in bone metabolism remains unclear.

Materials and Methods

Bone marrow mesenchymal stem cells (BMSCs)‐specific Alkbh1 knockout mice were used to investigate the role of Alkbh1 in bone metabolism. Western blot, qRT‐PCR, and immunofluorescent staining were used to evaluate the expression of Alkbh1 or optineurin (optn). Micro‐CT, histomorphometric analysis, and calcein double‐labeling assay were used to evaluate bone phenotypes. Cell staining and qRT‐PCR were used to evaluate the osteogenic or adipogenic differentiation of BMSCs. Dot blotting was used to detect the level of N6‐mA in genomic DNA. Chromatin immunoprecipitation (Chip) assays were used to identify critical targets of Alkbh1. Alkbh1 adeno‐associated virus was used to overexpress Alkbh1 in aged mice.

Results

Alkbh1 expression in BMSCs declined during aging. Knockout of Alkbh1 promoted adipogenic differentiation of BMSCs while inhibited osteogenic differentiation. BMSC‐specific Alkbh1 knockout mice exhibited reduced bone mass and increased marrow adiposity. Mechanistically, we identified optn as the downstream target through which Alkbh1‐mediated DNA m6A modification regulated BMSCs fate. Overexpression of Alkbh1 attenuated bone loss and marrow fat accumulation in aged mice.

Conclusions

Our findings demonstrated that Alkbh1 regulated BMSCs fate and bone‐fat balance during skeletal aging and provided a potential target for the treatment of osteoporosis.

Revealing oxidative stress-related genes in osteoporosis and advanced structural biological study for novel natural material discovery regarding MAPKAPK2

OBJECTIVES

This study aimed to find novel oxidative stress (OS)-related biomarkers of osteoporosis (OP), together with targeting the macromolecule Mitogen-activated protein kinase-activated protein kinase 2 (MAPKAPK2) protein to further discover potential novel materials based on an advanced structural biology approach.

METHODS

Gene expression profiles of GSE35958 were obtained from the Gene Expression Omnibus (GEO) database, which were included for weighted gene co-expression network analysis (WGCNA) and differential analysis to identify the most correlated module, to identify OS-related hub genes in the progression of OP. Functional annotations were also analyzed on the interested module to get a comprehensive understanding of these genes. Then, a series of advanced structural biology methods, including high-throughput screening, pharmacological characteristic prediction, precise molecular docking, molecular dynamics simulation, etc., was implemented to discover novel natural inhibitor materials against the MAPKAPK2 protein.

RESULTS

The brown module containing 720 genes was identified as the interested module, and a group set of genes was determined as the hub OS-related genes, including PPP1R15A, CYB5R3, BCL2L1, ABCD1, MAPKAPK2, HSP90AB1, CSF1, RELA, P4HB, AKT1, HSP90B1, and CTNNB1. Functional analysis demonstrated that these genes were primarily enriched in response to chemical stress and several OS-related functions. Then, Novel Materials Discovery demonstrated that two compounds, ZINC000014951634 and ZINC000040976869, were found binding to MAPKAPK2 with a favorable interaction energy together with a high binding affinity, relatively low hepatoxicity and carcinogenicity, high aqueous solubility and intestinal absorption levels, etc., indicating that the two compounds were ideal potential inhibitor materials targeting MAPKAPK2.

CONCLUSION

This study found a group set of OS-related biomarkers of OP, providing further insights for OS functions in the development of OP. This study then focused on one of the macromolecules, MAPKAPK2, to further discover potential novel materials, which was of great significance in guiding the screening of MAPKAPK2 potential materials.

CD137 Regulates Bone Loss via the p53 Wnt/β-Catenin Signaling Pathways in Aged Mice

Senile osteoporosis is a chronic skeletal disease, leading to increased bone brittleness and risk of fragile fractures. With the acceleration of population aging, osteoporosis has gradually become one of the most serious and prevalent problems worldwide. Bone formation is highly dependent on the proper osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) in the bone marrow microenvironment, which is generated by the functional relationship among different cell types, including osteoblasts, adipogenic cells, and bone marrow stromal cells in the bone marrow. It is still not clear how osteoporosis is caused by its molecular mechanism. With aging, bone marrow is able to restrain osteogenesis. Discovering the underlying signals that oppose BMSC osteogenic differentiation from the bone marrow microenvironment and identifying the unusual changes in BMSCs with aging is important to elucidate possible mechanisms of senile osteoporosis. We used 3 gene expression profiles (GSE35956, GSE35957, and GSE35959) associated with osteoporosis. And a protein-protein interaction (PPI) network was also built to identify the promising gene CD137. After that, we performed in vivo experiments to verify its function and mechanism. In this experiment, we found that significant bone loss was observed in aged (18-month-old) mice compared with young (6-month-old) mice. The adipose tissue in bone marrow cavity from aged mice reached above 10 times more than young mice. Combining bioinformatics analysis and vivo experiments, we inferred that CD137 might be involved in the p53 and canonical Wnt/β-catenin signaling pathways and thereby influenced bone mass through regulation of marrow adipogenesis. Importantly, osteoporosis can be rescued by blocking CD137 signaling in vivo. Our research will contribute to our understanding not only of the pathogenesis of age-related bone loss but also to the identification of new targets for treating senile osteoporosis.

Identification and validation of ferroptosis key genes in bone mesenchymal stromal cells of primary osteoporosis based on bioinformatics analysis

Primary osteoporosis has long been underdiagnosed and undertreated. Currently, ferroptosis may be a promising research direction in the prevention and treatment of primary osteoporosis. However, the specific mechanism of ferroptosis in primary osteoporosis remains a mystery. Differentially expressed genes (DEGs) were identified in bone mesenchymal stromal cells (BMSCs) of primary osteoporosis and heathy patients from the GEO databases with the help of bioinformatics analysis. Then, we intersected these DEGs with the ferroptosis dataset and obtained 80 Ferr-DEGs. Several bioinformatics algorithms (PCA, RLE, Limma, BC, MCC, etc.) were adopted to integrate the results. Additionally, we explored the potential functional roles of the Ferr-DEGs via GO and KEGG. Protein-protein interactions (PPI) were used to predict potential interactive networks. Finally, 80 Ferr-DEGs and 5 key Ferr-DEGs were calculated. The 5 key Ferr-DEGs were further verified in the OVX mouse model. In conclusion, through a variety of bioinformatics methods, our research successfully identified 5 key Ferr-DEGs associated with primary osteoporosis and ferroptosis, namely, sirtuin 1(SIRT1), heat shock protein family A (Hsp70) member 5 (HSPA5), mechanistic target of rapamycin kinase (MTOR), hypoxia inducible factor 1 subunit alpha (HIF1A) and beclin 1 (BECN1), which were verified in an animal model.

ADEIP: an integrated platform of age-dependent expression and immune profiles across human tissues

Gene expression and immune status in human tissues are changed with aging. There is a need to develop a comprehensive platform to explore the dynamics of age-related gene expression and immune profiles across tissues in genome-wide studies. Here, we collected RNA-Seq datasets from GTEx project, containing 16 704 samples from 30 major tissues in six age groups ranging from 20 to 79 years old. Dynamic gene expression along with aging were depicted and gene set enrichment analysis was performed among those age groups. Genes from 34 known immune function categories and immune cell compositions were investigated and compared among different age groups. Finally, we integrated all the results and developed a platform named ADEIP (http://gb.whu.edu.cn/ADEIP or http://geneyun.net/ADEIP), integrating the age-dependent gene expression and immune profiles across tissues. To demonstrate the usage of ADEIP, we applied two datasets: severe acute respiratory syndrome coronavirus 2 and human mesenchymal stem cells-assoicated genes. We also included the expression and immune dynamics of these genes in the platform. Collectively, ADEIP is a powerful platform for studying age-related immune regulation in organogenesis and other infectious or genetic diseases.

Age-related alterations and senescence of mesenchymal stromal cells: Implications for regenerative treatments of bones and joints

The most common clinical manifestations of age-related musculoskeletal degeneration are osteoarthritis and osteoporosis, and these represent an enormous burden on modern society. Mesenchymal stromal cells (MSCs) have pivotal roles in musculoskeletal tissue development. In adult organisms, MSCs retain their ability to regenerate tissues following bone fractures, articular cartilage injuries, and other traumatic injuries of connective tissue. However, their remarkable regenerative ability appears to be impaired through aging, and in particular in age-related diseases of bones and joints. Here, we review age-related alterations of MSCs in musculoskeletal tissues, and address the underlying mechanisms of aging and senescence of MSCs. Furthermore, we focus on the properties of MSCs in osteoarthritis and osteoporosis, and how their changes contribute to onset and progression of these disorders. Finally, we consider current treatments that exploit the enormous potential of MSCs for tissue regeneration, as well as for innovative cell-free extracellular-vesicle-based and anti-aging treatment approaches.

Cellular and Molecular Dynamics during Early Oral Osseointegration: A Comprehensive Characterization in the Lewis Rat

OBJECTIVE

There is a need to improve the predictability of osseointegration in implant dentistry. Current literature uses a variety of in vivo titanium (Ti) implantation models to investigate failure modes and test new materials and surfaces. However, these models produce a variety of results, making comparison across studies difficult. The purpose of this study is to validate an oral osseointegration in the Lewis rat to provide a reproducible baseline to track the inflammatory response and healing of Ti implants.

METHODS

Ti screws (0.76 mm Ø × 2 mm length) were implanted into the maxillary diastema of 52 adult male Lewis rats. Peri-implant tissues were evaluated 2, 7, 14, and 30 days after implantation (n = 13). Seven of the 13 samples underwent microtomographic analysis, histology, histomorphometry, and immunohistochemistry to track healing parameters. The remaining six samples underwent quantitative polymerase chain reaction (qPCR) to evaluate gene expression of inflammation and bone remodeling markers over time.

RESULTS

This model achieved a 78.5% success rate. Successful implants had a bone to implant contact (BIC)% of 68.86 ± 3.15 at 30 days on average. Histologically, healing was similar to other rodent models: hematoma and acute inflammation at 2 days, initial bone formation at 7, advanced bone formation and remodeling at 14, and bone maturation at 30. qPCR indicated the highest expression of bone remodeling and inflammatory markers 2-7 days, before slowly declining to nonsurgery control levels at 14-30 days.

CONCLUSION

This model combines cost-effectiveness and simplicity of a rodent model, while maximizing BIC, making it an excellent candidate for evaluation of new surfaces.

Comparison of Freshly Isolated Adipose Tissue-derived Stromal Vascular Fraction and Bone Marrow Cells in a Posterolateral Lumbar Spinal Fusion Model

STUDY DESIGN

Rat posterolateral lumbar fusion model.

OBJECTIVE

The aim of this study was to compare the efficacy of freshly isolated adipose tissue-derived stromal vascular fraction (A-SVF) and bone marrow cells (BMCs) cells in achieving spinal fusion in a rat model.

SUMMARY OF BACKGROUND DATA

Adipose tissue-derived stromal cells (ASCs) offer advantages as a clinical cell source compared to bone marrow-derived stromal cells (BMSCs), including larger available tissue volumes and reduced donor site morbidity. While pre-clinical studies have shown that ex vivo expanded ASCs can be successfully used in spinal fusion, the use of A-SVF cells better allows for clinical translation.

METHODS

A-SVF cells were isolated from the inguinal fat pads, whereas BMCs were isolated from the long bones of syngeneic 6- to 8-week-old Lewis rats and combined with Vitoss (Stryker) bone graft substitute for subsequent transplantation. Posterolateral spinal fusion surgery at L4-L5 was performed on 36 female Lewis rats divided into three experimental groups: Vitoss bone graft substitute only (VO group); Vitoss + 2.5 × 106 A-SVF cells/side; and, Vitoss + 2.5 × 106 BMCs/side. Fusion was assessed 8 weeks post-surgery via manual palpation, micro-computed tomography (μCT) imaging, and histology.

RESULTS

μCT imaging analyses revealed that fusion volumes and μCT fusion scores in the A-SVF group were significantly higher than in the VO group; however, they were not significantly different between the A-SVF group and the BMC group. The average manual palpation score was highest in the A-SVF group compared with the BMC and VO groups. Fusion masses arising from cell-seeded implants yielded better bone quality than nonseeded bone graft substitute.

CONCLUSION

In a rat model, A-SVF cells yielded a comparable fusion mass volume and radiographic rate of fusion to BMCs when combined with a clinical-grade bone graft substitute. These results suggest the feasibility of using freshly isolated A-SVF cells in spinal fusion procedures.Level of Evidence: N/A.

Hyaluronan Synthases' Expression and Activity Are Induced by Fluid Shear Stress in Bone Marrow-Derived Mesenchymal Stem Cells

During biomineralization, the cells generating the biominerals must be able to sense the external physical stimuli exerted by the growing mineralized tissue and change their intracellular protein composition according to these stimuli. In molluscan shell, the myosin-chitin synthases have been suggested to be the link for this communication between cells and the biomaterial. Hyaluronan synthases (HAS) belong to the same enzyme family as chitin synthases. Their product hyaluronan (HA) occurs in the bone and is supposed to have a regulatory function during bone regeneration. We hypothesize that HASes’ expression and activity are controlled by fluid-induced mechanotransduction as it is known for molluscan chitin synthases. In this study, bone marrow-derived human mesenchymal stem cells (hMSCs) were exposed to fluid shear stress of 10 Pa. The RNA transcriptome was analyzed by RNA sequencing (RNAseq). HA concentrations in the supernatants were measured by ELISA. The cellular structure of hMSCs and HAS2-overexpressing hMSCs was investigated after treatment with shear stress using confocal microscopy. Fluid shear stress upregulated the expression of genes that encode proteins belonging to the HA biosynthesis and bone mineralization pathways. The HAS activity appeared to be induced. Knowledge about the regulation mechanism governing HAS expression, trafficking, enzymatic activation and quality of the HA product in hMSCs is essential to understand the biological role of HA in the bone microenvironment.

Ubiquitin-specific protease 53 promotes osteogenic differentiation of human bone marrow-derived mesenchymal stem cells

The ubiquitin protease pathway plays important role in human bone marrow-derived mesenchymal stem cell (hBMSC) differentiation, including osteogenesis. However, the function of deubiquitinating enzymes in osteogenic differentiation of hBMSCs remains poorly understood. In this study, we aimed to investigate the role of ubiquitin-specific protease 53 (USP53) in the osteogenic differentiation of hBMSCs. Based on re-analysis of the Gene Expression Omnibus database, USP53 was selected as a positive regulator of osteogenic differentiation in hBMSCs. Overexpression of USP53 by lentivirus enhanced osteogenesis in hBMSCs, whereas knockdown of USP53 by lentivirus inhibited osteogenesis in hBMSCs. In addition, USP53 overexpression increased the level of active β-catenin and enhanced the osteogenic differentiation of hBMSCs. This effect was reversed by the Wnt/β-catenin inhibitor DKK1. Mass spectrometry showed that USP53 interacted with F-box only protein 31 (FBXO31) to promote proteasomal degradation of β-catenin. Inhibition of the osteogenic differentiation of hBMSCs by FBXO31 was partially rescued by USP53 overexpression. Animal studies showed that hBMSCs with USP53 overexpression significantly promoted bone regeneration in mice with calvarial defects. These results suggested that USP53 may be a target for gene therapy for bone regeneration.

MicroRNA‑338‑3p regulates age‑associated osteoporosis via targeting PCSK5

Bone loss is a disease that is highly associated with aging. This deleterious health condition has become a public concern worldwide, and there is an urgent need to discover more novel therapeutic strategies for the development of age‑associated osteoporosis. The present study aimed to explore the association between proprotein convertase subtilisin/kexin type 5 (PCSK5) and microRNA(miR)‑338‑3p in bone‑formation and bone‑loss processes. Western blotting assay and reverse transcription‑quantitative PCR were employed to analyze PCSK5 and miR‑338‑3p expression levels in bone mesenchymal stem cells (BMSCs). Dual‑luciferase reporter and RNA pull‑down assays were used to determine the target. For osteoblastic differentiation verification, alkaline phosphatase activity, osteocalcin secretion detection, bone formation‑related indicators (osterix, runt‑related gene 2, osteopontin and bone sialoprotein), hematoxylin and eosin staining and Alizarin Red S staining were performed. The findings of the present study indicated that the expression level of PCSK5 was higher in BMSCs from young rat samples, whereas the expression level of miR‑338‑3p was higher in BMSCs from samples of old rats. Experimental results also revealed that unlike miR‑338‑3p, downregulation of PCSK5 inhibited osteoblastic differentiation and osteogenesis by inhibiting alkaline phosphatase, osteocalcin, osterix, runt‑related transcription factor 2, osteopontin, bone sialoprotein and mineralized nodule formation. Overall, the results suggested that miR‑338‑3p could suppress age‑associated osteoporosis by regulating PCSK5.

Do polyunsaturated fatty acids protect against bone loss in our aging and osteoporotic population?

Age-related bone loss is inevitable in both men and women and there will soon be more people of extreme old age than ever before. Osteoporosis is a common chronic disease and as the proportion of older people, rate of obesity and the length of life increases, a rise in age-related degenerating bone diseases, disability, and prolonged dependency is projected. Fragility fractures are one of the most severe complications associated with both primary and secondary osteoporosis and current treatment strategies target weight-bearing exercise and pharmacological intervention, both with limited long-term success. Obesity and osteoporosis are intimately interrelated, and diet is a variable that plays a significant role in bone regeneration and repair. The Western Diet is characterized by its unhealthy components, specifically excess amounts of saturated fat intake. This review examines the impact of saturated and polyunsaturated fatty acid consumption on chronic inflammation, osteogenesis, bone architecture, and strength and explores the hypothesis that dietary polyunsaturated fats have a beneficial effect on osteogenesis, reducing bone loss by decreasing chronic inflammation, and activating bone resorption through key cellular and molecular mechanisms in our aging population. We conclude that aging, obesity and a diet high in saturated fatty acids significantly impairs bone regeneration and repair and that consumption of ω-3 polyunsaturated fatty acids is associated with significantly increased bone regeneration, improved microarchitecture and structural strength. However, ω-6 polyunsaturated fatty acids were typically pro-inflammatory and have been associated with an increased fracture risk. This review suggests a potential role for ω-3 fatty acids as a non-pharmacological dietary method of reducing bone loss in our aging population. We also conclude that contemporary amendments to the formal nutritional recommendations made by the Food and Nutrition Board may be necessary such that our aging population is directly considered.

Extracellular Vesicles in Musculoskeletal Pathologies and Regeneration

The incidence of musculoskeletal diseases is steadily increasing with aging of the population. In the past years, extracellular vesicles (EVs) have gained attention in musculoskeletal research. EVs have been associated with various musculoskeletal pathologies as well as suggested as treatment option. EVs play a pivotal role in communication between cells and their environment. Thereby, the EV cargo is highly dependent on their cellular origin. In this review, we summarize putative mechanisms by which EVs can contribute to musculoskeletal tissue homeostasis, regeneration and disease, in particular matrix remodeling and mineralization, pro-angiogenic effects and immunomodulatory activities. Mesenchymal stromal cells (MSCs) present the most frequently used cell source for EV generation for musculoskeletal applications, and herein we discuss how the MSC phenotype can influence the cargo and thus the regenerative potential of EVs. Induced pluripotent stem cell-derived mesenchymal progenitor cells (iMPs) may overcome current limitations of MSCs, and iMP-derived EVs are discussed as an alternative strategy. In the last part of the article, we focus on therapeutic applications of EVs and discuss both practical considerations for EV production and the current state of EV-based therapies.

Histological and Histomorphometric Analyses of Bone Regeneration in Osteoporotic Rats Using a Xenograft Material

We evaluated the effect of osteoporotic induction after eight weeks of initial healing of bone defects grafted with a xenograft material in a rat model. Bone defects were created in the femoral condyles of 16 female Wistar rats (one defect per rat). The defects were filled with bovine bone (Inter-Oss) granules. After eight weeks of bone healing, rats were randomly ovariectomized (OVX) or sham-operated (SHAM). At 14 weeks of bone healing, all animals were euthanized. Bone specimens were harvested and processed for histological and histomorphometric analyses to assess new bone formation (N-BF%), remaining bone graft (RBG%) and trabecular bone space (Tb.Sp%) within the defect area. After 14 weeks of bone healing, histological evaluation revealed a significant alteration in trabecular bone in OVX rats compared to SHAM rats. There was lower N-BF% in OVX rats (22.5% ± 3.0%) compared to SHAM rats (37.7% ± 7.9%; p < 0.05). Additionally, the RBG% was significantly lower in OVX (23.7% ± 5.8%) compared to SHAM (34.8% ± 9.6%; p < 0.05) rats. Finally, the Tb.Sp% was higher in OVX (53.8% ± 7.7%) compared to SHAM (27.5% ± 14.3%; p < 0.05) rats. In conclusion, within the limitations of this study, inducing an osteoporotic condition in a rat model negatively influenced bone regeneration in the created bone defect and grafted with a xenograft material.